[NewAKGGuy]

 
Quote:

 
That's not the part I reponded to. It was this "Amplifiers (including small ones in portable devices) have no problem providing the required voltage. Their limitation is current. If your amplifier isn't capable of providing enough current, the voltage sags, compromising the sound. Because this happens preferentially at certain frequencies, this affects your frequency response."  Either you don't understand what you said here or specifically chose to ignore it and it's completely wrong and contradicts the running out of voltage for high impedances.

 
Actually, I think this part of Jim's response is correct.  It's definitely the case for Home-Fi.  I'm not an electrical engineer, nor am I a physicist, but I did work in the high-end audio business for many years and in that time I never saw an 8 or 16ohm rated speaker that was a real challenge for just about any off the shelf El Cheapo receiver to drive.  Conversely if you wanted to drive large planar speakers with 4 and 2 ohm impedance ratings, and impedance curves that dipped down to .5 ohms at some frequencies (read Martin Logan Sequel II etc), that's when you needed the massive Krells, Spectrals, and Mark Levinsons that could drive the required voltages into a (virtual) dead short.  It was our understanding (albeit propagated by the amp manufacturers) that wattage output is a function of both current and voltage and that it's relatively easy and cheap to build an amplifier that achieves a high wattage output but with little ability to deliver current, but much more difficult and expensive to build an amplifier that delivers high wattage and current.  In my experience, if you have two speakers with the same efficiency rating, it requires a sturdier and more thoroughly built amplifier to drive the lower impedance speakers than it does the higher impedance speakers, and consequently I would assume that lower impedance speakers are more difficult to dive, holding efficiency equal.
       

 

[goodvibes]

It's current to drive those low impedances but in the case of Logans, a more complex reactance is also involved. The problem seems more through the x-over range where it uses a lot of music energy and drops below 3 ohms with some phase angle. It never gets below 1 ohm and that's at 20k hz where there's almost no energy. They also easily fool some protection circuits. I always wondered why somebody would design a transformer coupled speaker that way. What the Sequel II does is prove my point about frequency response and impedance. They are not directly related if you look at graphs of both and this is a severe example of what would be at the limit of acceptable load. http://www.stereophile.com/content/martinlogan-sequel-ii-loudspeaker-measurements 
 
 I never disagreed that more current is needed to drive a low impedance load. I clearly stated as much early on and never said different. It just doesn't relate to frequency response. Look, I understand that Jim may have just crossed streams with power response for a moment and misspoke as we all do but he took it further with grammar and credentials which have absolutely nothing to do with this discussion. I'm not new to this either.

 

[High_Q]

I've made some edits to my post to make it more precise and clearer.  Now I got to find out how Amps tightens the sound in addition to making it louder?  Damping?  

 
 

 

[JimAustin]

Quote:

 
 I never disagreed that more current is needed to drive a low impedance load. I clearly stated as much early on and never said different. It just doesn't relate to frequency response.

Decided to check in this morning, so I'll answer this. It just isn't true. Impedance is frequency dependent, as you know. If by this you mean that the relationship between frequency response and impedance is not simple, then you are correct. But impedance -- it's magnitude and phase angle -- determine the demand for current. When the amplifier cannot meet this current demand (because it cannot produce enough power), the voltage falls. This is a frequency-dependent phenomenon, and it's why you need a bigger amplifier to drive a demanding load. If the amplifier isn't up to the task, the amps inability to generate sufficient current leads to changes in the frequency response. 
 
On the other hand -- and this is what I think you got wrong at first, or perhaps just didn't express clearly -- voltage limitations in an amplifier determine only the accessible volume. If your amplifier is capable of delivering sufficient volume through the high-impedance speakers/cans you're using, your frequency response will be as it was designed to be.
 
To summarize: Insufficient voltage leads to inadequate volume (and clipping distortion when you push it too hard). Insufficient current leads to changes in the frequency response.
 
I wouldn't be surprised to learn that we're saying more or less the same thing, just conceptualizing it -- and expressing it -- in different ways. But who knows?
 
Jim

 

[goodvibes]

Welcome back

. It's not my contention that impedance and frequency response aren't at all related as with extremely high impedance output amplifiers and low impedance transducers you can have loss of energy at the extremes but that's true even even at lower volumes. I just don't think it's directly related when we're talking in practical terms of acceptable impedance matching. I think the Sequels a good example of an impedance limit where any frequency effect is still rather negligible. These items are designed for flat response with the impedance curve that have and an appropriate source. I think the appropriate source may be the sticking point.
 
I said earlier that I thought it perhaps the perspective of this that may have us at odds but I didn't want folks here to get too caught up in impedance mismatches for gear that was designed to work together. You'd be amazed at the extrapolation we can have here.
 
 My Ipod touch 3G is odd man out here as with a 1 ohm output impedance will dip at the extremes when driving very low impedance IEMs but it does it at any volume and it's not the norm for modern DAPs so I also understand the relationship of unacceptable impedance matching. Once you get over about a 20-1 ratio which should near the minimum for solid state and practically the lowest anybody here would ever see in their portable kit, everything should work out to where we would only be discussing efficiency and clipping. I also suspect we're not that far off. Basically, look for efficiency and not impedance when choosing and that you may need more efficiency in a higher impedance phone to match maximum volume level from a DAP.

 

[JimAustin]

 
Quote:

 Basically, look for efficiency and not impedance when choosing and that you may need more efficiency in a higher impedance phone to match maximum volume level from a DAP.

Yep. And I agree that people shouldn't worry as much about impedance matching. I don't come to this forum often, but I still see a ton of misinformation. My beef is with the people who contend that you should avoid 300 ohm 'phones for portable devices, without ever noting their efficiency, then recommending something that's 32 ohms as a better match for a portable device that may have a tiny power output and a relatively high output impedance. Sure, it may be fine, but it's not better.
 
I'm glad we worked this out.

 

[goodvibes]

 

[ericp10]

Hello koonhua90. Are you still enjoying your JH16?
 
Quote:

Thanks for the reply everyone, but then what about the current provided to the low impedance phones, as said by ClieOS. I believe in what he said, as in that to provide the same power when resistance is lower, the current has to increase.

But the thing is, impedance is not exactly resistance, it's the imaginary part of resistance. I think that the signal should have a varying voltage and current, as opposed to having constant voltage or current, right? Please correct me if I am wrong.

The reason I posted this thread is because I find that both my Samsung Yp-Z5 and Ipod nano need a very high volume (60-70% of max volume) to even drive Monster Miles Davis and IE8 (both dynamic) properly. But when I used balanced armature phones, I can achieve same volume at a lower volume on the players.

 

 

[NewAKGGuy]

Thanks guys for clearing things up quite a bit for those of us who are less intellectually dexterous with electrical engineering!  I really should dig a bit and learn more about the science given my interest in the hobby, but there never seems to be enough time with all the monetary and fiscal chicanery that's about these days.  And that's a topic on which I do have some expertise if anyone wants to discuss the mass fraud which is being foisted upon us elsewhere...